An electrospray ionization source for the Micromass Quattro II tandem quadrupole mass spectrometer has been constructed for use with low flow rates (nL/min), comparable to what has been described by Mann et al. as nanospray. The system includes two cameras for positioning the needle (tip) and observation of the flow. Because the geometry of the ion source housing of the Quattro II instrument has restricted access to this region, several designs had to be tested before acceptable performance was achieved. A heater for the nitrogen line also was installed and tested for use with aqueous and other less volatile solvents. The system has so far been utilized for the ESI-MS and ESI MS/MS analysis of native and derivatized oligosaccharides and glycoconjugates, peptides and proteins.